shred: Implemented --force option (#2012)

tests/by-util/test_shred.rs

@@ -1 +1,51 @@
-// ToDO: add tests
+use crate::common::util::*;
+
+#[test]
+fn test_shred_remove() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    let file_a = "test_shred_remove_a";
+    let file_b = "test_shred_remove_b";
+
+    // Create file_a and file_b.
+    at.touch(file_a);
+    at.touch(file_b);
+
+    // Shred file_a.
+    scene.ucmd().arg("-u").arg(file_a).run();
+
+    // file_a was deleted, file_b exists.
+    assert!(!at.file_exists(file_a));
+    assert!(at.file_exists(file_b));
+}
+
+#[cfg(not(target_os = "freebsd"))]
+#[test]
+fn test_shred_force() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    let file = "test_shred_force";
+
+    // Create file_a.
+    at.touch(file);
+    assert!(at.file_exists(file));
+
+    // Make file_a readonly.
+    at.set_readonly(file);
+
+    // Try shred -u.
+    let result = scene.ucmd().arg("-u").arg(file).run();
+    println!("stderr = {:?}", result.stderr);
+    println!("stdout = {:?}", result.stdout);
+
+    // file_a was not deleted because it is readonly.
+    assert!(at.file_exists(file));
+
+    // Try shred -u -f.
+    scene.ucmd().arg("-u").arg("-f").arg(file).run();
+
+    // file_a was deleted.
+    assert!(!at.file_exists(file));
+}